A breathing bag is used as a breathing aid in the presence of smoke or toxic fumes, for getting out of a house on fire, for example. A high pressure cylinder of oxygen may be attached to the bag to provide oxygen for a limited period of time. Whether an oxygen cylinder is provided or not, exhaled air contains a substantial amount of oxygen, and it is possible to re-breathe exhaled air several times in an emergency situation.
It is known that ambient air contains about 21% oxygen. It is also known that a recommended minimum oxygen content in breathable air is about 15%, because a lower amount could cause hallucinations. It is further known that a person breathing normally consumes about 5% of the oxygen present in ambient air, while a person hyperventilating in a panic situation absorbs only about 3%. Therefore, it is believed that in many circumstances, the air exhaled into a breathing bag still contains oxygen and can be re-breathed again. When the breathable gas in the high pressure cylinder is a mixture of gas rich in oxygen, such as 90% oxygen for example, this gas can be re-breathed several times before it reaches the 15% lower limit.
Several types of closed-circuit breathing bags can be found in the prior art. Examples of the prior art breathing devices are described in the following documents:    U.S. Pat. No. 896,447 issued to S. S. Hall et al. on Aug. 18, 1908;    U.S. Pat. No. 4,154,234 issued to R. L. Baker on May 15, 1979;    U.S. Pat. No. 4,164,218 issued to F. E. Martin on Aug. 14, 1979;    U.S. Pat. No. 4,362,153 issued to J. G. Wilson et al., on Dec. 7, 1982;    U.S. Pat. No. 4,586,500 issued to M. H. Glynn on May 6, 1986;    U.S. Pat. No. 4,794,923 issued to J. A. Bartos on Jan. 3, 1989;    U.S. Pat. No. 4,817,597 issued to S. Tanaka on Apr. 4, 1989;    U.S. Pat. No. 4,821,711 issued to W. Eckstein et al., on Apr. 18, 1989;    U.S. Pat. No. 4,879,996 issued to V. H. Harwood, Jr. et al., on Nov. 14, 1989;    U.S. Pat. No. 4,917,081 issued to J. A. Bartos on Apr. 17, 1990;    U.S. Pat. No. 4,938,211 issued to M. Takahashi et al., on Jul. 3, 1990;    U.S. Pat. No. 5,165,394 issued to J. Hochberg on Nov. 24, 1992;    U.S. Pat. No. 5,720,279 issued to Y. Furuichi et al., on Feb. 24, 1998;    U.S. Pat. No. 5,724,958 issued to B. Farnworth et al., on Mar. 10, 1998;    U.S. Pat. No. 6,279,571 issued to R. Meckes on Aug. 28, 2001;    U.S. Pat. No. 6,761,162 issued to L. J. Swann on Jul. 13, 2004;    U.S. Pat. No. 7,028,687 issued to M. Silver et al., on Apr. 18, 2006;    CA Patent 713,356 issued to I. Streimer on Jul. 13, 1965;    CA Patent 787,696 issued to L. R. Phillips on Jun. 18, 1968;    CA Patent 1,020,840 issued to L. Yi-Sheng et al., on Nov. 15, 1977;    CA Patent Appl. 2,024,439 filed by F. W. Arnoth, on Aug. 31, 1991; This application was published on Mar. 2, 1991;
The apparatus of the prior art are presented herein only to show the state of the art in the field of the invention. These apparatus are characterized in that they have either a carbon dioxide scrubber mounted therein between an exhaled air compartment and a breathable air compartment, or an oxygen-generating canister therein, in which carbon dioxide and moisture in exhaled air enter into a chemical reaction with the content of the canister to produce oxygen.
At least one breathing bag of the prior art has the option to re-breath the content of the bag several times. This breathing bag is described in a patent granted to the inventor of the present emergency breathing bag. This patent is identified as follows:
U.S. Pat. No. 7,047,966 issued to Robert E. Stewart on May 23, 2006.
While the apparatus of the prior art have their own merits, the prior art literature in the field of breathing devices does not disclose the possibility of purifying re-breathable gas by stratification in a breathing device. Stratification of gases is well known in the mining industry for example, as explained in:
U.S. Pat. No. 4,512,610 issued to Clark J. Gilbert et al. on Apr. 23, 1985. This document discloses the fact that blowers are used in mines to prevent stratification of gases in the mine atmosphere.
Although the phenomenon of separating gases by stratification is known generally, the prior art is silent concerning the possibility of purifying air by stratification in a breathing apparatus for increasing the quality of re-breathable air in that apparatus.